The present invention is an improvement in the storm mapping system disclosed in U.S. Pat. No. 4,023,408, the disclosure of which is incorporated herein by reference.
In the referred to patent, several significant advances in the field of storm mapping and the display of storm information were disclosed. While the device described in the referenced patent has met a significant commercial need, it has been discovered that at least a segment of those with a need for storm mapping do not need the high resolution capability offered by the device described therein. Thus, in order to benefit that specific segment of the public it was found desirable to provide a device with capabilities very similar to that described in the referenced patent, with the exception that display resolution is somewhat more limited than that in the described device. One advantage of offering reduced resolution is a significant reduction in complexity, and hence cost.
The device described in the referenced patent offers a theoretically infinite number of display locations distributed 360.degree. in azimuth about the origin or observation location and extending out to the full range (100-200 nautical miles) of the instrument. In contrast, the improved storm mapping device of this invention displays .+-.60.degree. in azimuth, in 15.degree. increments and divides the 100 nautical mile range into three increments, for a total of 27 display segments; nine azimuth segments for each of three different ranges, 0-30 miles, 30-60 miles, and 60-100 miles. A particular advantage of reducing the resolution is that rather than organizing the memory to store data representing each different electrical disturbance, and storing data defining the coordinates of the disturbance, as in the referenced patent, the storage system of the present invention need only provide a storage register or memory location for each of the different display segments.
The device described in the referenced patent provided storm intensity information by displaying a plurality of received signals closely spaced together. In accordance with the present invention each of the 27 different display segments assumes one of four states; dark, indicating no activity; steadily illuminated, indicating relatively low activity or low intensity; slowly flashing, indicating increased intensity or activity; and rapidly flashing indicating relatively high intensity or activity. In order to effect this on the display, each display segment corresponds to a different storage register or location in a digital memory. Each time a received signal is detected corresponding to a particular display segment, and thus to a particular storage location or register, the data in the register is incremented by a determined quantity. Although the determined quantity by which each storage register is incremented could be equal, in accordance with a further feature of the invention the closer is the display segment to the origin, the greater is the amount by which the data is incremented. Intensity is determined by the quantity in the storage register or location at any time, and in order to maintain a correlation between this quantity and actual electrical activity, the storage registers are continually decremented. While the data in the storage register could be decremented at a constant rate, in accordance with a further feature of the invention, the storage registers are decremented in sequence, but the amount by which they are decremented depends upon the pre-existing quantity in the storage location.
Accordingly, the display process is relatively simple, it only requires, for each storage location determining the data stored therein and controlling the associated display element to either be unilluminated, steadily illuminated, slowly flashing or rapidly flashing.
The analog processing of received signals is similar to that described in the referred to patent. More particularly, three tuned receivers are provided, one omnidirectional receiver for sensing electric field (sometimes referred to as the sense channel) and two orthogonal magnetic field receivers. The three receivers or channels are tuned in common to approximately 50 KHz. The signals in the sense and magnetic field channels are amplified, and then the signal in the sense channel is correlated with the signals in the two magnetic field channels to produce two correlated signal channels.
The two correlated signals are summed as vectors and if the resulting sum exceeds a threshold a timer is initiated, the timer generating a plurality of control signals at specified delays for purposes which will be described hereinafter.
One use of the control signals produced by the timer is for the synchronous detection or correlation of the signals. A second use of the control signals is to control an integration process on the correlated signals. The integrated correlated signals are summed to provide a range approximation signal.
A plurality of comparators are provided with this range approximation signal and the output of the comparators comprise a digital range approximation signal. The analog to digital conversion is arranged to perform the foldback process described in the referred to patent. More particularly, the analog to digital conversion of the range approximation signal produces a two bit range representative digital signal as well as an inhibit signal if the detected range is outside the range of the instrument (either less than 5 miles or greater than 100 miles). Significantly, in connection with the foldback process, the relatively large range approximation signals produce the relatively smaller digital representations. For example, the largest range approximation signal output (within the range of the instrument) produces the two bit digital signal--"00" whereas the smallest range approximation within the range of the instrument produces a two bit digital signal "11".
At the same time, the outputs of the two magnetic channels comprising the correlated integrated signals are provided to a second set of comparators for an analog to digital conversion of azimuth representing signals. The second set of comparators produces a four bit digital signal defining azimuth as within one of nine segments as well as contributing to the generation of the inhibit signal if the azimuth is detected as being outside the range of the instrument.
Once the seven bits of azimuth and range information, as well as an eighth inhibit bit is available, another one of the control signals from the timer is used to initiate the logic circuit, including a storage section or memory. In one embodiment of the invention which has been constructed, the logic circuit is implemented as a conventional microprocessor, for example, INTEL 8748. The seven data bits generated by the instrument are used to address the memory so as to locate a storage location in the microprocessor corresponding to the region in which the electrical disturbance resulting in the received signals is located. This storage location has stored therein data representing the electrical activity and the particular received signal is now employed to modify the data stored at that location. While that modification could be simply incrementing a quantity stored there, in a preferred form of the invention the amount by which the previously stored data is incremented depends upon the particular location being addressed. Thus, those locations closest to the origin are incremented by more than other locations which may be further from the origin. For example, the range locations furthest from the origin may be incremented by a given amount each time a signal is detected as originating in that range segment. The next closer range segment is incremented by twice that quantity each time a signal is detected as originating in that range. Still a closer range segment is incremented by double the previous amount. And finally, signals representing closest activity to the origin are incremented by still double that amount.
Since intensity is a time dependent parameter, each of the storage locations is also continually being decremented so that a display is not saturated by "old" intensity information. Rather than decrementing each storage location at a constant rate, each storage location is operated on sequentially but the quantity removed from that storage location is related to the pre-existing stored data. Thus, those locations which have indications of relatively intense activity are reduced by more, on each iteration, than other locations which represent less intense activity.
On a repetitive basis, as a result, the display apparatus comprising a display chip (HLCD0438P) is driven by the microprocessor, each display segment is driven depending on the stored quantity so that the display segment is either undisturbed, steadily illuminated, or flashed at a slow or rapid rate.
In summary then, the invention comprises a system for detecting and displaying relative locations of sources of electrical disturbances generated by weather phenomena with respect to an observation location comprising:
receiving means for receiving electrical signals generated by said electrical disturbances in a predetermined frequency band and for producing received signals related thereto,
timing means responsive to said received signals for producing a plurality of control signals,
processing means responsive to said received signals and to said control signals for producing processed signals relating said received signals in a frame of reference whereby relatively larger received signals are related closer to an origin of said frame of reference comprising said observation location than relatively smaller received signals,
logic means, including storage means, reponsive to said control signals and said processed signals for storing data representing said processed signals at locations determined by said processed signals, and
display means driven by said logic means for displaying said stored data representing relative locations of said electrical disturbances to said frame of reference.